Why does the diesel generator's tank lid have a small air hole?

During the use of the generator set , the user found a small air hole above the fuel tank cover. What are the reasons for this?

The small air holes above the fuel tank cover will cause air and dust to enter the tank. However, if the fuel tank cover is sealed, a vacuum will form inside the tank during the drop in the oil quantity in the tank. This will affect the suction pump from sucking fuel properly. .

At high temperatures, the fuel will evaporate and the pressure inside the tank will increase during the evaporation process. If the lid of the tank is sealed, then the tank will break and there will be a small air hole, which will balance the pressure difference inside and outside the tank.

The fuel tank cover of the diesel generator set must have a small air hole. This small air hole can ensure that the diesel generator is in a stable working state without other failures and will not affect its normal use.